The present invention relates to a drier for pasta.
As is known, and in the following description and the subsequent claims, dry pasta generally means pasta with a water content of between 11.5 and 12.5% by weight.
In order to produce dry pasta, one generally starts with a dough of durum wheat flour or semolina and water or eggs which, for reasons of good handling and machinability, must have a water content of 30-32% by weight and this value is then brought to the desired value of 11.5-12.5% by a suitable drying process.
It is recognised that the organoleptic and nutritive characteristics of the dry pasta produced, as well as its ability to withstand cooking which, as is well known, affect the commercial value of the finished product, are affected by the way in which such a process is carried out.
The ability to withstand cooking is correlated to a known parameter called the cooking factor. This parameter takes account of the chewability, palatability, consistency and organoleptic characteristics of the pasta after cooking. In this connection, the pasta must have good chewing strength (it should not be hard or stick to the teeth) but should have the consistency typical of so-called "al dente" pasta, it should be slippery and flexible in the dish, and it should not develop a patina which makes its surface sticky or glutinous.
Another important factor associated with the drying method is constituted by the danger of the nutritive properties (in particular the essential aminoacids) of the pasta being degraded by heat, the extent of this degradation being considered by many to depend on the drying temperature and period.
For these reasons, methods of drying fresh pasta are amongst the methods and processes which have been investigated most and have received greatest technical attention in the food-science field.
This is shown, amongst other things, by the host of patents published on an international scale on the subject of methods of drying fresh pasta.
For example, amongst the drying methods established for some time in the art, the best known is carried out entirely at a low temperature within the range of between 40.degree. and 60.degree. C. The organoleptic and nutritive qualities of the dry pasta thus produced remain almost unaltered but, according to some critics, it has high acidity and a poor cooking factor which adversely affect its commercial qualities.
Another equally widespread method, which was established in order to overcome the long periods of time (of the order of 16-24 hours) required to carry out the method mentioned above and to reduce the considerable lengths of the driers needed as a result, provides for treatment at very high temperatures of up to 110-120.degree. C. Whilst this method of treatment can drastically reduce the dimensions of the driers, the nutritional and organoleptic properties of the durum wheat semolina used cannot always be kept intact since they may be altered substantially by the high temperatures which, in particular, cause thermal degradation of the essential aminoacids in the dry pasta produced.
According to another method established by the present applicant, the drying is carried out in a plurality of successive isothermal heat-treatment stages, with a gradual increase of the temperature within the range of from 40.degree. to 110.degree. C.
All these methods and all the variants and different characteristics of the methods implemented by the numerous producers have required the design, production and setting-up of corresponding driers or at least the substantial modification of existing driers.
This situation, which is not at all rational from a commercial and technical point of view, is likely to be further complicated in view of continuing investigations into the nature and intrinsic characteristics of pasta, and into the variability of these characteristics in dependence on the type of ingredients used, and of the constantly increasing knowledge and/or interpretations of the chemical/physical phenomena which take place during the drying of pasta.